DE102021214699A1 - motor vehicle - Google Patents

Abstract

Motor vehicle (1), comprising a drive train (6) which has at least one electrical machine (2) which can be connected or is connected to an electrical energy store (3) which can be charged by means of a charging interface from an external charging device, which electrical machine (2) is designed for this purpose to generate a torque and to transmit it to an output (7) of the drive train (6), a decoupling device (10) being provided which is designed to mechanically decouple the electric machine (2) from the to decouple the output (7), wherein in the decoupling state a rotational movement of the rotor (8) of the electric machine (2) in a desired charging orientation (19) of the rotor (8) is decoupled from the output (7) of the drive train (6).

Description

The invention relates to a motor vehicle, comprising a drive train, which has at least one electrical machine that can be connected or is connected to an electrical energy store that can be charged by an external charging device by means of a charging interface, which is designed to generate torque and transmit it to an output of the drive train.

Motor vehicles which have electrical machines as drive devices, which electrical machines can be supplied with electrical energy via an electrical energy store, are known in principle from the prior art. In addition to being charged during operation by means of recuperation, such electrical energy stores can be charged by an external charging device via a charging interface when the motor vehicle is at a standstill. Examples of such an external charging device can be a charging station or a so-called “wall box”.

In this regard, it is known to use the inverter of the motor vehicle, which is used to operate the electric machine, for charging from a DC voltage source, namely the charging device. Additional inductances are required for switching the DC/AC inverter into a DC/DC converter, and these are expediently provided by the coils of the electrical machine.

During the charging process, the torque that is caused by the rotor due to the energization for charging the electrical energy store depends on the orientation of the rotor or the rotor position. Since the rotor position or the orientation of the rotor is ultimately random when the motor vehicle is parked on the external charging device, it must be ensured that such a torque cannot lead to an undesired movement of the motor vehicle, so that safety problems are ruled out. Nevertheless, for example when the motor vehicle is held in place by a parking brake and/or a parking lock or other transmission locks, the rotor causes a torque that is introduced into the drive train. Since the rotor position or the orientation of the rotor, as described, adjusts itself randomly, in the worst case, torques can be generated in the range of the maximum torque of the electric machine, which can have a negative effect on the service life of the components of the drive train.

The invention is based on the object of specifying a motor vehicle that is improved in comparison thereto, in which, in particular, the execution of charging processes on an external charging device is improved.

The object is achieved by a motor vehicle having the features of claim 1. Advantageous configurations are the subject matter of the dependent claims.

As described in the introduction, the invention relates to a motor vehicle that has a drive train with an electric machine and an electric energy store. The electrical energy store can be charged by a charging interface of the motor vehicle on an external charging device. The electric machine is primarily used to generate torque and to transmit it to an output of the drive train. The electrical machine can thus be understood as a drive device or traction drive. The invention is based on the finding that the motor vehicle has a decoupling device which is designed to mechanically decouple the electric machine from the output when required in order to carry out a charging process in a decoupling state, wherein in the decoupling state a rotary movement of the rotor of the electric machine is converted into a Desired charging orientation of the rotor is decoupled from the output of the drive train.

In this case, the electric machine is designed in such a way that, in a first state, it generates a torque that can be transmitted to an output of the drive train and, in a second state, to transmit current from a charging interface to an electrical energy store. The torque can be transmitted, for example, via a reduction gear. In the second state, for example, the coils of the electric motor can be used as part of a step-up converter, also known as a boost converter. The second state can also be called the decoupling state. $$\begin{array}{l}//\text{first state}=\text{traction operation}\\ //\text{decoupling state}=\text{state in which it is loaded}=\text{second state}\end{array}$$

In other words, the invention provides a decoupling device that can bring about mechanical decoupling between the output and the electrical machine, in particular can decouple the rotor of the electrical machine from the output. Decoupling can be performed to perform a charging operation. For example, the decoupling can be carried out when or before initiating a charging process, so that a rotational movement of the rotor of the electric machine into a target charging orientation of the rotor is possible, during which rotational movement the rotor is decoupled from the rest of the drive train, in particular from the output. The decoupling device thus makes it possible for the rotor to be rotated, in particular in the target charging orientation, without generating a torque on the rest of the drive train. Instead of using the rotor in the randomly present position to carry out the charging process, as is usual in the prior art, the decoupling device is used, as described, to decouple the rotor and thus a defined rotary movement of the rotor is decoupled from the output of the Execute drive train so that the rotor can be moved to the target loading orientation.

The target charging alignment designates in particular that alignment of the rotor or that rotor position in which the rotor causes a comparatively small torque, in particular no torque, during the charging process. It can thus be ensured that when the charging process is carried out, no torque or only a comparatively small torque is caused by energizing the rotor. Safety-relevant rotary movements of the rotor and the transmission of torque to the drive train, which ultimately have to be blocked, can thus be ruled out. On the one hand, this increases safety when carrying out charging processes as well as the service life of the drive train and its components.

The decoupling device described herein can in principle be configured in any way, as long as the decoupling device can carry out a mechanical coupling if required, in particular when activated by a control device, so that the rotor can be decoupled from a part of the drive train, in particular as close as possible to the rotor, from the output of the drive train . The decoupling device can be understood as a "mechanical separation point" since it can mechanically separate the drive train. The decoupling device can be designed, for example, as a clutch device or as a freewheel.

If the decoupling device is designed as a clutch device, it can optionally be designed as a form-fitting clutch device or as a friction clutch, specifically as a claw clutch or multi-plate clutch. As described, the decoupling device must enable decoupling between the rotor and the output, it being sufficient to enable decoupling in a defined direction of rotation, for example when using a freewheel. The decoupling device thus allows the rotor angle to be changed without applying torque to the wheels. If the motor vehicle is put into a charging mode, for example, the decoupling device can first cancel the coupling of the rotor, so that the rotor can be brought into the desired target charging orientation, in which the charging process can advantageously be carried out, with no or only a low torque being generated by the charging process and applied to the rotor.

According to one embodiment of the motor vehicle, it can be provided that the decoupling device is designed to lock the rotor of the electric machine after assuming the desired charging alignment, in particular by means of a separate locking device or by establishing the coupling to the output. As described, the rotor is primarily decoupled from the output of the drive train in order to perform a rotational movement that converts the rotor into the desired target charging orientation. Once the rotor is in the target loading orientation, the decoupling device can lock the rotor in the target loading orientation.

For this purpose, the decoupling device can restore the previously canceled coupling of the rotor, ie couple the rotor back to the rest of the drive train. It is also possible to provide a separate locking device, for example a parking brake or a parking lock or the like, which acts additionally or alternatively on the rotor in order to lock it. The separate locking device can also be integrated into the electric machine in such a way that the rotor can be locked in order to prevent the rotor from deflecting from the desired charging orientation during the charging process. The locking of the rotor after assuming the target charging alignment has the effect, in particular, that rotational movements of the rotor when the charging process is started, for example due to transient processes, are prevented. The rotor is therefore locked, so that rotational movements due to transient processes or deviations from the target charging alignment in the charging process, which could cause the target charging alignment to be left, can be blocked.

According to a further embodiment of the motor vehicle, it can be provided that the decoupling device is designed to brace the rotor of the electric machine after assuming the target charging alignment by applying a defined pretensioning torque in the drive train. The bracing of the rotor in the drive train out of the desired charging alignment can in particular provide that the pretensioning torque is generated by means of the current flow during the charging process. In other words, the target charging orientation can be selected such that, in particular after the rotor has been locked, for example by coupling to the rest of the drive train, a comparatively low torque is produced which prestresses the rotor in the drive train in a defined manner.

The defined prestressing or the application of the defined prestressing torque, in particular, prevents the torque from oscillating or torque oscillating around the zero point during the charging process. By applying the preload torque, the rotor is given a preferred direction in which the comparatively defined small torque can be applied. The preload torque can be <10% of the maximum machine torque, for example, with a range of less than 5% of the maximum machine torque being desirable. For example, a freewheel can be used as a decoupling device or a freewheel can form part of the decoupling device, it being possible to ensure by applying the preload torque that the rotor remains locked against the freewheel, which is connected to the rest of the drive train. The selection of the preload torque can ultimately be selected as a function of the specific electric machine and the drive train. For example, the point at which the decoupling device or the rotor is arranged in the drive train can also be included. Due to the fact that the rotor is prestressed by the defined prestressing torque, deviations from the desired charging alignment, which cause comparatively greater torques, are prevented in particular.

As described above, the decoupling device can in principle have any desired coupling devices. According to one embodiment, the decoupling device can have at least one claw clutch or be designed as such, with the claw clutch having a defined number of teeth, in particular 30 to 70 teeth, with a control device of the motor vehicle being designed to determine the target loading alignment as a function of a current tooth arrangement . When using the claw coupling, the number of teeth and the arrangement of the teeth of the counterparts or the individual claws of the claw coupling relative to one another determine which relative orientations can be adopted.

In other words, a first claw, which is connected to the rotor of the electric machine, cannot be brought into engagement with a second claw, which is connected to the output of the drive train, in arbitrary orientations. The teeth each have teeth and tooth gaps, with the two claws only being able to be brought into engagement if the teeth of the first claw can be introduced into tooth gaps in the second claw and vice versa. The control device described can determine the target charging orientation in which the rotor is to be placed for the charging process as a function of a current tooth arrangement. For example, it can be determined in which orientation the rotor should ideally be brought and which target loading orientation can be implemented. In other words, it can be determined which tooth engagement or which rotor alignment comes closest to the desired target charging alignment. If the rotor is locked, that meshing or that orientation of the first claw relative to the second claw can be selected which allows the target loading orientation of the rotor to be approximated as closely as possible.

As previously described, the rotor can generally be preloaded after or to assume the desired loading orientation in the drive train in order to avoid torque oscillations about the zero point. According to a further refinement, the previously described control device or a further control device of the motor vehicle can be designed to set the target charging orientation by prestressing the rotor. In other words, the desired prestressing of the rotor can be included in the definition or determination of the target charging orientation. This does not affect the principle of assuming the target charging orientation described at the outset. If the target charging alignment is assumed, a comparatively small torque should nevertheless be effected on the rotor or be effected by the rotor, which, however, specifies a preferred direction for the rotor and avoids oscillation around the zero point of the torque. In other words, the target charging orientation is selected in a defined manner such that the rotor is prestressed by a low torque or prestressing torque in the drive train.

The configurations with regard to the prestressing of the rotor and the consideration of the possible tooth engagements can be combined with one another as desired. In other words, it can be taken into account which tooth meshes are fundamentally possible and which prestressing of the rotor is desired. In this way, the target charging alignment or the possible target charging alignments of the rotor, which can depend on a number of pole pairs or, in principle, a symmetry of the rotor, can be determined. It can then be determined which meshing of the teeth of the first claw and the second claw enable the target charging orientation(s) to be assumed.

In this case, it can also be taken into account whether a prestressing of the rotor should be applied or can be applied, for example in order to correct target positions that are specified by the claw engagements and do not correspond exactly to the target charging alignment. From the combination of possible tooth engagements and a possible prestressing of the rotor, the target charging alignment can thus be carried out for almost all rotor angles. In this case, an interval of possible preload torques can be defined, so that a preload torque is selected from the interval of possible preload torques depending on the possible tooth engagements, in order to achieve the target charging alignment starting from a target position. The preload torques can be applied in both directions of rotation of the rotor, so that a positive or negative preload torque can be applied to achieve the target loading alignment.

In particular, it can also be taken into account that the preload torque does not fall below a minimum torque. For this purpose, for example, a tooth meshing can be implemented that does not represent the tooth meshing closest to the target loading alignment, but rather, for example, a relative rotation of the first claw to the second claw by a further tooth meshing from the target loading alignment. The tooth engagement described can be selected in order to be able to apply at least the minimum torque as a preload torque in order to subsequently move the rotor into the target charging alignment.

As described, the motor vehicle described can have at least one vehicle axle that is driven or can be driven by the electric machine. According to a further embodiment, the motor vehicle can also have at least two driven or drivable vehicle axles. In this case, the decoupling device can be assigned to that vehicle axle whose inverter is designed or used to carry out a charging process. The design provides for the mechanical separation point to be provided on the rotor of that electrical machine whose inverter is also used to carry out the charging process. For example, a first vehicle axle can be driven by a first electrical machine that is assigned a first inverter. A second vehicle axle may be powered by a second electric machine controlled by a second inverter. Depending on whether the electrical energy store is charged by the components of the first vehicle axle or the second vehicle axle during a charging process, the decoupling device can be assigned to the first or the second vehicle axle.

As described, the motor vehicle can have one or more control devices. At least one of the control devices can be designed to control the at least one inverter for carrying out the charging process and/or to control the decoupling device and/or to control a separate decoupling device of the coupling device. The control device can, for example, control the inverter in such a way that the currents conducted through the inductances of the rotor can be adapted to the charging process or the reaction that occurs as a result. Furthermore, the decoupling device can be controlled, for example in order to decouple the rotor from the rest of the drive train or to restore the coupling. The separate coupling device described above, which can be provided in particular for fixing the rotor, can also be controlled by the control device. The locking device can be designed, for example, as a parking lock or as a parking brake.

The motor vehicle can also be further developed such that at least one detection device is provided, which is designed to detect a coupling state of the rotor. In other words, the detection device can detect whether the rotor is coupled to the rest of the drive train or whether the rotor is coupled to the output or decoupled from it. It is thus possible to detect whether the coupling between the rotor and the output has been established or whether it has been decoupled, for example by correspondingly switching the decoupling device into the decoupling state. This makes it possible to determine whether there is a rotary connection between the electric machine and the wheels or whether this is interrupted. The detection device can also be designed to detect the position of the rotor or the alignment of the rotor or the rotor position. The detection device can do this For example, use a rotor position sensor or determine the position using current sensors. A table that can be stored in a control device can be used, for example, to determine the target charging orientation. Depending on the number of pole pairs or the symmetry of the rotor, several target charging orientations or several rotor angles can be possible.

At least one control device of the motor vehicle can change the desired charging alignment when a change in the rotor position is detected, in particular during a charging process. In other words, the control device can, for example when the detection device detects a rotational movement of the rotor during the charging process, adapt a control intervention, in particular change the activation of the inverter, in order to prevent an undesired rotational movement of the rotor. Furthermore, appropriate control signals can be sent to the decoupling device, for example to lock the rotor.

In addition, the invention relates to a method for carrying out a charging process of an electrical energy store of a motor vehicle, in particular a motor vehicle as described above, an electric machine of the motor vehicle being transferred to a decoupling state in order to carry out a charging process, in which the electric machine, in particular the rotor, is driven by an output of the motor vehicle is decoupled, wherein in the decoupling state a rotational movement of the rotor of the electric machine is performed in a target charging orientation, in which rotational movement of the rotor is decoupled from the output. In other words, the method can be carried out on the motor vehicle described above. All the advantages, details and features that have been described in relation to the motor vehicle can be fully transferred to the method.

• 1 eine Prinzipdarstellung eines Kraftfahrzeugs nach einem ersten Ausführungsbeispiel;
• 2 eine Prinzipdarstellung eines Kraftfahrzeugs nach einem zweiten Ausführungsbeispiel; und
• 3 eine Prinzipdarstellung einer Sollladeausrichtung.

The invention is explained below using exemplary embodiments with reference to the figures. The figures are schematic representations and show:

• 1 a schematic diagram of a motor vehicle according to a first embodiment;
• 2 a schematic diagram of a motor vehicle according to a second embodiment; and
• 3 a schematic diagram of a target loading alignment.

1 shows a schematic section of a motor vehicle 1, which has an electric machine 2, an electric energy store 3, an inverter 4 and a control device 5. The electric machine 2 is integrated into a drive train 6 of the motor vehicle 1, which has an output 7 which, as shown only by way of example, leads to a wheel. The electrical machine 2 has a schematically indicated rotor 8 whose coils can be controlled or supplied with current by the inverter 4 . Furthermore, the motor vehicle 1 has a charging interface 9, via which the motor vehicle 1, in particular the electrical energy store 3, can be connected to an external charging device, for example a charging station, which is not shown in detail.

The motor vehicle 1 also has a decoupling device 10 which is designed to decouple or decouple the electric machine 2, in particular the rotor 8, from the rest of the drive train 6. For example, the decoupling device 10 is designed as a freewheel or as a clutch device, in particular as a positive-locking clutch device. The arrangement of the decoupling device 10 in a sideshaft assigned to the wheel is merely an example. A corresponding decoupling device 10 could also be arranged in an output shaft 11 of the electric machine 2, for example. The output 7 is that part of the drive train 6 which lies in the torque flow between the wheel and the rotor 8 . In principle, any part of the drive train 6 to which torque can be applied by the electric machine 2 when the decoupling device 10 is closed and from which the rotor can be decoupled can be understood as an output.

The decoupling device 10 thus decouples the rotor 8 from the rest of the drive train 6, so that the rotor 8 can be rotated without transmitting torque to the rest of the drive train 6, in particular without transmitting torque to the output 7 or the wheels.

If a charging process is to be carried out in which a current from the external charging device is used to charge the electrical energy store 3 of the motor vehicle 1, the inverter 4 is ultimately used as a DC/DC converter, with the coils of the rotor 8 being used as inductances . The control device 5 is designed to individually control the individual switches of the inverter 4, for example three high-side and three low-side switches of the inverter 4.

In order to avoid that when the current is conducted through the rotor 8, a torque is generated which is transmitted to the output 7 or the drive train 6 and would either lead to a movement of the motor vehicle 1 or, if the motor vehicle 1 was fixed, a load on the Could form drive train 6, the rotor 8 is transferred to a target charging orientation. For this purpose, the rotor 8 is first decoupled from the rest of the drive train 6 by the decoupling device 10 . The decoupling device 10 forms a mechanical separation point which causes a mechanical decoupling of the rotor 8 . When the rotor 8 rotates, no torque is generated on the remaining drive train 6 . The rotor 8 can thus be rotated arbitrarily and placed in a target charging orientation.

The decoupling device 10 can then restore the coupling to the drive train 6 . For example, the rotor 8 can be blocked as a result, or a separate blocking device (not shown in detail) can be used additionally or alternatively in order to generate the blocking effect on the rotor 8 . A parking brake or a parking lock 22 or a means of the electrical machine 2 that can mechanically lock the rotor 8 can be understood as an example of a separate locking device.

In the locked state or the re-coupled state of the rotor 8, the charging process can be carried out. Since the rotor 8 has been brought into the target charging alignment, it is ensured that no torque or only a small torque, for example below 10% of the maximum machine torque, is applied to the rotor 8 or the output shaft 11 by the energization in the charging process.

The control device 5 is also coupled to a detection device 13 . The detection device 13 is designed to detect the orientation of the rotor 8 and is only connected to a rotor position sensor by way of example. In addition or as an alternative to the rotor position sensor, it is also possible for the detection device 13 to be able to detect the orientation of the rotor 8 based on sensor values from current sensors. If, for example, a movement of the rotor 8 during the charging process is detected by the detection device 13, the inverter 4 can be controlled accordingly by means of the control device 5 in order to adjust the charging process, so that rotational movements or the generation of torque on the rotor 8 can be reduced accordingly.

2 shows a second exemplary embodiment of a motor vehicle 1, which has two driven or drivable vehicle axles 12, 12'. Each of the vehicle axles 12, 12' is thus assigned an electrical machine 2, 2'. In this exemplary embodiment, only the electric machine 2 assigned to the first vehicle axle 12 is used to charge the shared electric energy store 3, through which both electric machines 2, 2' can be fed. In this case, only the inverter 4 that is assigned to the electrical machine 2 is used as a DC/DC converter. The decoupling device 10 is therefore arranged in the part of the drive train 6 which has the vehicle axle 12 . As shown, the decoupling device 10 is arranged closer to the electric machine 2 in this exemplary embodiment, for example directly on or on the drive shaft 11. The basic function of the decoupling device 10 or the implementation of the charging process is completely dependent on the description 1 transferable.

3 shows part of the decoupling device 10 in an axial view. As described, the decoupling device 10 can in principle also be embodied as a coupling device, in particular a form-fitting coupling device, for example as a claw coupling. In this case, the decoupling device 10 may include first and second claws that are engageable with each other and disengageable to decouple the rotor.

A first claw 14, which can be brought into engagement with a second claw (not shown in detail), is shown purely by way of example. The first claw 14 has teeth 15 distributed circumferentially on the first claw 14 and spaced apart by tooth gaps 16 . In this embodiment, the two claws are designed differently, i.e. the teeth 15 are made smaller in the circumferential direction than the teeth of the second claw corresponding to the tooth gaps 16 of the first claw 14 . The embodiment shown is merely exemplary. Instead of the two claws, the transmission element that is connected to the rotor 8 can also be a sliding sleeve or other transmission elements that allow selective coupling to the output 7 .

When the first claw 14 is coupled to the second claw, the teeth 15 of the first claw 14 engage in the tooth gaps of the second claw. Correspondingly, the teeth of the second claw engage in the Tooth gaps 16 of the first claw 14 a. The tooth gaps 16 thus define angular ranges in which engagement of the corresponding teeth is possible. In other words, the decoupling device 10 can only be closed again when the teeth 15 can engage in corresponding tooth gaps. Since the relative orientation of the first claw 14 relative to the second claw ultimately results randomly from the movement of the motor vehicle 1 and the rotor 8, the orientation or the possible engagement positions can be included in the determination of the target loading alignment.

For example, it can be determined which engagement positions are fundamentally possible and into which position or by which rotor angle the rotor 8, which is coupled to the first claw 14, for example, must be rotated in order to achieve the target loading alignment. An angle 17 by which the center points of the teeth 15 are spaced apart in the circumferential direction is shown purely by way of example.

It can be seen that the number of teeth 15 and their extent in the circumferential direction determine the angle 17 . The number of teeth 15 or the corresponding tooth gaps accordingly determines the positions in which the individual teeth 15 can be engaged in the corresponding tooth gaps.

An initial position 18 is shown purely as an example, in which the rotor 8 and, together with the rotor 8, the first claw 14 are located, for example the situation in which the motor vehicle 1 is parked for charging. Furthermore, in 3 a desired loading orientation 19 of the first claw 14 is shown, the desired loading orientation 19 also applying to the rotor 8 which is connected to the first claw 14 as described. The control device 5 can then determine a target position 20 into which the first claw 14 can be rotated together with the rotor 8 relative to the second claw. Ultimately, this defines the tooth engagement that is to be used for assuming the target loading alignment 19 .

In addition, a preload angle 21 is shown, by which the drive train 6 can be rotated by applying a defined preload torque to the rotor 8 in order to assume the target loading orientation 19 . The prestressing of the rotor 8 or of the drive train 6 relates to the translations and elasticities present in the drive train 6 . In principle, the rotor 8 can be rotated by a defined angle, which is referred to as the preload angle 21 , in order to preload the rotor 8 . For this purpose, a defined low preload torque, for example below 10% of the maximum machine torque of the electric machine 2, can be used. This allows in particular that oscillations or fluctuations of the rotor 8 or the torque around a zero point of the torque can be prevented.

The application of the prestressing moment can be applied in particular taking into account the possible meshing of the teeth. Depending on the angle through which the rotor 8 has to be rotated in order to achieve the target charging orientation 19, it may be necessary to apply a specific preload angle 21. The preload angle 21 can vary, so that after assuming the desired tooth engagement, for example the target position 20, which is closest to the target loading alignment 19, the remaining angle is applied by the preloading, so that the target loading alignment 19 can be achieved as optimally as possible. Depending on how many teeth the claw 14 has, arbitrarily fine subdivisions of the angle are possible. If a minimum torque is to be realized as the pretensioning torque, a desired position 20 can also be selected which is not the tooth engagement which is closest to the desired loading alignment 19 . Instead, an adjacent tooth engagement can be selected as the target position 20, so that the minimum torque can be implemented as the preload torque.

The advantages, details and features shown in the individual exemplary embodiments can be arbitrarily interchanged, transferred to one another and combined with one another.

Reference List

1

motor vehicle

2

electric machine

3

electrical energy storage

4

inverter

5

control device

6

powertrain

7

downforce

8th

rotor

9

charging interface

10

decoupling device

11

output shaft

12, 12'

vehicle axle

13

detection device

14

claw

15

Tooth

16

tooth gap

17

angle

18

starting position

19

target loading orientation

20

target position

21

preload angle

22

parking lock

Claims (10)

Motor vehicle (1), comprising a drive train (6) which has at least one electrical machine (2) which can be connected or is connected to an electrical energy store (3) which can be charged by means of a charging interface from an external charging device, which electrical machine (2) is designed for this purpose in a first state to generate a torque that can be transmitted to an output (7) of the drive train (6) and in a second state to transmit electricity from a charging interface to an electrical energy storage device, characterized by a decoupling device (10) which is used for this purpose is designed to mechanically decouple the electric machine (2) from the output (7) for carrying out a charging process in a decoupling state, if necessary, wherein in the decoupling state a rotary movement of the rotor (8) of the electric machine (2) in a desired charging alignment (19) of the rotor (8) is decoupled from the output (7) of the drive train (6). Motor vehicle (1) after claim 1 , characterized in that the decoupling device (10) is designed to lock the rotor (8) of the electric machine (2) after assuming the desired charging orientation (19), in particular by means of a separate locking device and/or by establishing the coupling to the output (7). Motor vehicle (1) after claim 1 or 2 , characterized in that the decoupling device (10) is designed to brace the rotor (8) of the electric machine (2) after assuming the desired charging alignment (19) by applying a defined biasing torque in the drive train (6). Motor vehicle (1) according to one of the preceding claims, characterized in that the decoupling device (10) has at least one claw clutch or is designed as such, the claw clutch having a defined number of teeth, in particular 30-70 teeth (15), with a control device (5) of the motor vehicle (1) is designed to determine the target loading alignment (19) as a function of a current tooth arrangement. Motor vehicle (1) according to one of the preceding claims, characterized in that a control device (5) of the motor vehicle (1) is designed to set the desired charging orientation (19) by prestressing the rotor (8). Motor vehicle (1) according to one of the preceding claims, characterized by two driven or drivable vehicle axles (12, 12 '), wherein the decoupling device (10) of that driving tool axis (12, 12 ') is assigned, whose inverter (4) is designed to carry out a charging process. Motor vehicle (1) according to one of the preceding claims, characterized by at least one control device (5) which is designed to control the at least one inverter (4) for carrying out the charging process and/or to control the decoupling device (10) and/or to control a separate blocking device of the decoupling device (10). Motor vehicle (1) according to one of the preceding claims, characterized by at least one detection device (13) which is designed to detect a coupling state of the rotor (8). Motor vehicle (1) after claim 8 , characterized in that at least one control device (5) is designed to change the desired charging orientation (19) when a change in a rotor position is detected, in particular during a charging process. Method for carrying out a charging process of an electrical energy store (3) of a motor vehicle (1), in particular a motor vehicle (1) according to one of the preceding claims, characterized in that an electric machine (2) of the motor vehicle (1) for carrying out a charging process in a decoupling state is transferred, in which the electric machine (2), in particular the rotor (8) is decoupled from an output (7) of the motor vehicle (1), wherein in the decoupling state a rotational movement of the rotor (8) of the electric machine (2) is carried out in a desired charging orientation (19), during which rotary movement the rotor (8) is decoupled from the output (7).

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